Short fibrillar cellulose ester material (termed fibrets) are employed in a variety of applications such as in the manufacture of tobacco smoke filters and as a replacement for clay and titanium dioxide in paper opacification. Fibrets can be produced using an unstable wet spinning process in which the fibrets are precipitated out of an organic solution of the polymer and formed, in a nonsolvent, under controlled shearing conditions. The formed fibrets are in a mixture of the organic solvent and nonsolvent. The mixture is then screened or filtered to increase the fibret concentration and the fibret concentrate thereafter heated to evaporate the organic solvent. The solvent is separated by distillation from the solvent-nonsolvent mixtures withdrawn from the screening or filtering and the fibret concentrate forming steps.
In the precipitation step, a large volume of nonsolvent is required which must be heated. Additionally, large distillation capacity is required to separate the solvent from the nonsolvent in the mixtures of such solvent and nonsolvent withdrawn from the filter and fibret concentration steps. Thus, it would be desirable to reduce the energy and capital costs associated with the precipitation and subsequent distillation steps.